Medical diagnostic apparatus and medical analysis method

ABSTRACT

According to one embodiment, a medical diagnostic apparatus includes processing circuitry and display circuitry. The processing circuitry estimates a position of a structure in a subject based on data obtained by scanning with respect to the subject and analyzes tissue characterization in the subject. The display circuitry displays an analysis result of the tissue characterization obtained by the processing circuitry with respect to a plurality of positions in the subject except for the estimated structure position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2016-047833, filed Mar. 11,2016, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a medical diagnosticapparatus, which scans the inside of the living body to create atomographic image of an organ or the like and is related to diagnosis ofdiseases, and a medical analysis method.

BACKGROUND

An ultrasonic diagnosis apparatus is a diagnosis apparatus whichdisplays an image of intravital information. Compared to other imagediagnosis apparatuses such as an X-ray diagnosis apparatus and an X-raycomputed tomography (CT) apparatus, the ultrasonic diagnosis apparatusis inexpensive and is free from exposure, and is utilized as a usefulmedical diagnostic apparatus for observation in real time in anoninvasive manner. The range of applications of the ultrasonicdiagnosis apparatus is wide. The ultrasonic diagnosis apparatus isapplied to diagnosis of a circulatory organ such as the heart, theabdominal region such as the liver and kidney, peripheral blood vessels,obstetrics and gynecology, and breast cancer.

The ultrasonic diagnosis apparatus usually visualizes the morphology ofthe body tissue by expressing the magnitude of the amplitude of anultrasonic reception signal (echo signal) in luminance. However, it hasbeen reported in various reports that an ultrasonic reception signalcontains other various types of physical information. Various attemptshave been made to clinically apply some of the physical informationcontained in the ultrasonic reception signal.

For example, a statistical quantity of an amplitude of an echo signal iscalculated, and a relationship between a mean value and a variance valueis analyzed, whereby a content of a microstructure which is less likelyto be visually judged can be quantified. In recent years, there has beenused a so-called ultrasonic elastography method of analyzing a localmoving amount of an organ in a subject and thereby presenting physicalinformation such as the hardness or elastic modulus of the organ. Theultrasonic elastography method also utilizes phase information containedin an ultrasonic signal before image creation.

A body tissue has specific attenuation characteristics. Ultrasonic wavesapplied to a subject propagate inside the living body while beingattenuated. At this time, when the attenuation amount of the ultrasonicwaves having propagated inside the living body is large, there occurs aphenomenon in which a sufficient echo signal cannot be received in themiddle of scanning. On the other hand, features of a body tissue areoften monitored by observing an attenuation state of the echo signal.For example, there has been known a method of analyzing a change in echobrightness in transmitting and receiving directions to quantify anultrasonic attenuation amount of a target object. Taking the liver as anexample, usefulness is expected, particularly in quantitative diagnosisof fatty liver. Specifically, a subject in which an echo signal isextremely reduced is presumed to be a fatty liver containing many fatdroplets in the liver. Similar results may be obtained in a case ofliver cirrhosis.

Thus, a plurality of methods for quantitatively diagnosing theultrasonic attenuation amount have been proposed. For example, aplurality of ultrasonic pulses having different center frequencies aretransmitted and received, and a plurality of obtained signals arecompared with regard to how much the intensities of the signals changein a depth direction. There is a method of estimating the attenuationamount specific to a subject based on this comparison. It is known thatthe ultrasonic attenuation amount inside the living body is differentdepending on frequencies. Thus, a value specific to a target tissue isobtained by comparing changes in intensities of a plurality of frequencysignals. Further, by virtue of the use of a broadband pulse, an effectsimilar to the above effect can be obtained by transmitting andreceiving an ultrasonic sound once per one of ultrasonic transmittingand receiving directions.

However, in this method, since a signal of a high frequency (harmonic)component is generated when a signal in a low frequency regionpropagates in a tissue, it is considered that the generated highfrequency component becomes an error when the attenuation amountspecific to a subject is estimated. Thus, there has been also proposed amethod of transmitting two pulses, in which positive and negative of awaveform of a transmitted ultrasonic wave are inverted, to a subject ina single ultrasonic transmitting direction, performing a differenceoperation on an obtained reception signal, and thereby removing a highfrequency component generated during propagation of an ultrasonic wave.

Further, there has been proposed that a color display reflecting themagnitude of the attenuation amount is performed using the obtainedsignals of frequency components. For example, different color phases areassigned to the attenuation amounts corresponding to the respectivefrequency components and are superposed on a B mode image. Consequently,user can visually grasp the magnitude of the attenuation amount withhigh accuracy by watching a magnitude of a change in color phase in adepth direction. A similar effect can be obtained by performing a colormapping according to a signal intensity difference between two differentfrequency components. Since an attenuation constant at each point in across section is obtained by differentiating the signal intensitydifference between two frequency components in the depth direction, themagnitude of the attenuation constant can be colored and displayed.

In all of the methods described in the prior art, the attenuation amountis estimated by calculating the signal intensity of a reception signalor a change in frequency characteristics in the depth direction. Theestimation of the attenuation amount is based on the fact thatcomposition and distribution of a scatterer are uniform in the depthdirection. However, many different tissues mixedly exist in an actualliving body, whereby the living body has a complicated structure. Thus,there are few portions constituted of the uniform scatterers asdescribed above. For example, in the liver, even if there is a portionlooking like a uniform speckle in the range of several centimeters, whena focusing range is widened, structures that can be visually recognized,such as blood vessels, an abdominal wall, and a gall bladder, enter afocusing region.

In such structures, brightness of a signal is significantly differentfrom a peripheral uniform substantial portion, and in addition, thereflection characteristics are also different. Thus, it is consideredthat the frequency component included in a reception signal issignificantly different. Accordingly, in both the method of analyzingthe change in brightness and the method of analyzing the frequencycomponent, when the structure, as described above, havingcharacteristics different from the periphery is included in an analysistarget region, assumption as a premise of the estimation of theattenuation amount is not established. Consequently, there is a problemthat although some numeric values can be calculated in the analysistarget region, the calculated values have low reliability.

Namely, in both of the above methods, when a remarkable structure isincluded in the analysis target region, a brightness distribution andfrequency characteristics near the structure are different from theperiphery, so that the attenuation amount sometimes cannot be accuratelycalculated.

For example, as shown in FIG. 11, an extremely high or low attenuationamount value is calculated in a region including, in the analysis targetrange, a portion exhibiting reflection characteristics and scatteringcharacteristics different from the parenchyma of the liver, like anabdominal wall and a diaphragm. In such a case, the calculatedattenuation amount value is considered to be not a result representingthe attenuation amount of a target object but an artifact generated by astructure.

From the above, for quantification of the attenuation amount with highaccuracy, in a clinical field, there is required a procedure in which across section being as inconspicuous in a structure as possible is set,and a uniform region is selected from the set cross section to set theanalysis target region. However, judgement in the setting of theanalysis target region is left to an operator's subjective view. Thus,there is a problem that the accuracy of the setting of the analysistarget region and reproducibility cannot be secured. In addition, it issometimes difficult to select a region suitable for analysis, and tomake matters worse, it takes a long time, so that there is a problemthat this is a burden for an operator. Namely, it is a burden for theoperator to draw a cross-section avoiding a structure or select auniform region in which a quantification result is likely to be reliablein quantification, and highly accurate diagnosis may be difficult.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram showing a configuration of anultrasonic diagnosis apparatus as a medical diagnostic apparatusaccording to the present embodiment.

FIG. 2 is a B-mode image according to the present embodiment on which avariance ratio R_(τ) is to be superimposed in the color phasecorresponding to a value of the variance ratio R_(τ).

FIG. 3 is a view showing an example of a variance ratio superimpositionimage in which the variance ratio R_(τ) is superimposed on the B-modeimage of FIG. 2 in a scanned region being the same as the scanned regionconcerning the variance ratio R_(τ) in the color phase corresponding tothe value of the variance ratio R_(τ).

FIG. 4 is a view showing an attenuation superimposition image accordingto the present embodiment displayed on a monitor, together with alegend.

FIG. 5 is a flowchart showing an example of a processing procedureaccording to the present embodiment concerning a structure estimationfunction and a tissue characterization analysis function.

FIG. 6 is a flowchart showing an example of a processing procedureconcerning the structure estimation function and the tissuecharacterization analysis function according to a variation of thepresent embodiment.

FIG. 7 is a view showing a first application of the present embodimentand showing an example in which when it is determined that measurementof a representative value in measurement ROI1 is appropriate andmeasurement of a representative value in measurement ROI2 is notappropriate, a representative value or a predetermined notificationcorresponding to the name of measurement ROI and an attenuationsuperimposition image on which the measurement ROI is superimposed aredisplayed on the monitor.

FIG. 8 is a flowchart showing an example of a processing procedureconcerning a representative value calculation function according to thefirst application of the present embodiment.

FIG. 9 is a view showing a second application of the present embodimentand showing an example in which representative values and the ranks ofreliability corresponding to the names of the measurements ROI and anattenuation superimposition image on which the measurements ROI aresuperimposed are displayed on the monitor.

FIG. 10 is a flowchart showing an example of a processing procedureaccording to the second application of the present embodiment concerninga reliability display function.

FIG. 11 is a view according to the prior art.

DETAILED DESCRIPTION

In general, according to one embodiment, a medical diagnostic apparatusincludes processing circuitry and display circuitry. The processingcircuitry estimates a position of a structure in a subject based on dataobtained by scanning with respect to the subject and analyzes tissuecharacterization in the subject. The display circuitry displays ananalysis result of the tissue characterization obtained by theprocessing circuitry with respect to a plurality of positions in thesubject except for the estimated structure position.

Hereinafter, a medical diagnostic apparatus according to the presentembodiment will be described with reference to the drawings. The medicaldiagnostic apparatus according to the present embodiment may be anyapparatus as long as it is noninvasive (for example, a magneticresonance imaging (MRI) apparatus). In order to specifically describethe medical diagnostic apparatus according to the present embodiment,the medical diagnostic apparatus will be described as an ultrasonicdiagnosis apparatus. Note that the same reference numerals in thefollowing description denote constituent elements having substantiallythe same configurations, and a repetitive description will be made onlywhen required.

FIG. 1 is a configuration diagram showing a configuration of anultrasonic diagnosis apparatus 1 as the medical diagnostic apparatusaccording to the present embodiment. As shown in FIG. 1, the ultrasonicdiagnosis apparatus 1 has an ultrasonic probe 3, an input apparatus 5, amonitor 7, and an apparatus body 9. In addition, the ultrasonicdiagnosis apparatus 1 may be connected to a biological signal measurer(not shown) typified by an electrocardiograph, phonocardiograph,sphygmograph, or respiration sensor, an external storage apparatus (notshown), and a network via interface circuitry 27.

The ultrasonic probe 3 has a plurality of piezoelectric transducers, amatching layer, and a backing material provided on the back face side ofthe piezoelectric transducers. The piezoelectric transducers areacoustic/electric reversible conversion elements such as piezoelectricceramic elements. The plurality of piezoelectric transducers arearranged in parallel and mounted on the distal end of the ultrasonicprobe 3. Assume that in the following description, one piezoelectrictransducer forms one channel. Each piezoelectric transducer generates anultrasonic wave in response to a drive signal supplied from ultrasonictransmission circuitry 11 to be described later. When ultrasonic wavesare transmitted to a subject P via the ultrasonic probe 3, thetransmitted ultrasonic waves (hereinafter referred to as thetransmission ultrasonic waves) are reflected by a discontinuity surfaceof acoustic impedance of a living body tissue in the subject.

The piezoelectric transducers receive the reflected ultrasonic waves andgenerate an echo signal. The amplitude of the echo signal depends on anacoustic impedance difference on the discontinuity surface as a boundaryconcerning the reflection of the ultrasonic waves. In addition, thefrequency of the echo signal generated when transmission ultrasonicwaves are reflected by a moving blood flow and the surface of thecardiac wall or the like shifts depending on the velocity component ofthe moving body (the blood flow and the surface of the cardiac wall) inthe ultrasonic transmitting direction due to the Doppler effect.

Hereinafter, the ultrasonic probe 3 will be described as a probe whichtwo-dimensionally scans a scanned region with a one-dimensional arrayconstituted of one-dimensionally arranged piezoelectric transducers. Theultrasonic probe 3 may be a mechanical four-dimensional probe whichexecutes three-dimensional scanning by swinging a one-dimensional arrayin a direction perpendicular to the array direction of a plurality oftransducers. The ultrasonic probe 3 is not limited to a mechanicalfour-dimensional probe and may be a two-dimensional array probe.

The matching layer is provided on the ultrasonic wave radiation surfaceside of the piezoelectric transducers to improve the efficiency oftransmission and reception of ultrasonic waves to and from the subjectP. The backing material prevents ultrasonic waves from propagatingbackward from the piezoelectric transducers.

The input apparatus 5 is connected to the apparatus body 9 via theinterface circuitry 27. The input apparatus 5 includes various types ofswitches, buttons, a trackball, a mouse, and a keyboard which are usedto input, to the apparatus body 9, various types of instructions andconditions, an instruction to set a region of interest (ROI), varioustypes of image quality conditions, setting instructions, and the likefrom an operator. The input apparatus 5 may include a touch pad on whichan operation surface is touched to perform input operation, a touchpanel display in which a display screen and the touch pad areintegrated, and microphone. The input apparatus 5 corresponds to aninput portion or input interface circuitry.

The input apparatus 5 inputs a start instruction (hereinafter referredto as an attenuation quantification start instruction) for executing afunction (hereinafter referred to as a structure estimation function) ofcomprehensively executing a setting function 291 to be described laterand an estimation function 293 to be described later and subsequentlyexecuting a function (hereinafter referred to as a tissuecharacterization analysis function) of comprehensively executing a gainreverse correction function 295 to be described later, a sound fieldcharacteristic correction function 297 to be described later, and ananalysis function 299 to be described later. At this time, a signalconcerning the input of the attenuation quantification start instructionis output to processing circuitry 29 to be described later.

The input apparatus 5 is not limited to an input device provided withonly physical operation parts such as a mouse and a keyboard. Examplesof the input apparatus 5 include an electric signal processing circuitwhich receives an electric signal corresponding to an input operationfrom an external input device provided separately from the ultrasonicdiagnosis apparatus 1 and outputs the received electric signal tovarious circuits.

The monitor 7 displays morphological information in the living body,blood flow information, and the like as images based on video signalsoutput from image generating circuitry 19, image compositing circuitry23, and so on. The monitor 7 displays analysis results obtained by theanalysis function 299. For example, a CRT display, a liquid crystaldisplay, an organic EL display, an LED display, a plasma display, or anyother display known in the relevant technical field can be suitably usedas the monitor. The monitor 7 corresponds to a display unit or displaycircuitry.

The apparatus body 9 has ultrasonic transmitting circuitry 11,ultrasonic receiving circuitry 13, B-mode processing circuitry 15,Doppler processing circuitry 17, image generating circuitry 19, an imagememory 21, image compositing circuitry 23, storage circuitry 25,interface circuitry 27, and processing circuitry (central processingunit) 29.

The ultrasonic transmitting circuitry 11 has a pulse generator 111,transmission delay circuitry 113, and pulser circuitry 115. Theultrasonic transmitting circuitry 11 is an example of an ultrasonictransmission unit and may have a processor. The pulse generator 111repeatedly generates rate pulses for the formation of transmissionultrasonic waves at a predetermined rate frequency fr Hz (period: 1/frsec). The generated rate pulses are distributed to channel counts andsent to the transmission delay circuitry 113.

The transmission delay circuitry 113 gives each rate pulse a delay time(hereinafter referred to as a transmission delay time) necessary tofocus a transmission ultrasonic wave into a beam and determinetransmission directivity for each of the plurality of channels. Thestorage circuitry 25 stores the transmission direction of transmissionultrasonic waves or the transmission delay time concerning thetransmission direction (hereinafter referred to as a transmission delaypattern). The processing circuitry 29 refers to the transmission delaypattern stored in the storage circuitry 25 when ultrasonic waves aretransmitted.

The pulser circuitry 115 applies a voltage pulse (drive signal) to eachof the transducers of the ultrasonic probe 3 at the timing based on thisrate pulse. According to this constitution, an ultrasonic beam istransmitted to the subject P.

The ultrasonic transmitting circuitry 11 transmits ultrasonic waves(hereinafter referred to as ultrasonic waves for attenuationquantification) to the subject P based on attenuation quantificationconditions in response to generation of B-mode data to be describedlater corresponding to one frame. The attenuation quantificationconditions are transmission conditions for generation of the ultrasonicwaves for attenuation quantification and reception conditions forreception of the ultrasonic waves for attenuation quantification. Thetransmission conditions include a transmission center frequency of theultrasonic wave for attenuation quantification and a transmissionbandwidth of the ultrasonic wave for attenuation quantification. Thereception conditions include a reception center frequency of theultrasonic wave for attenuation quantification and a reception bandwidthof the ultrasonic wave for attenuation quantification. The attenuationquantification conditions are stored in the storage circuitry 25.

The transmission conditions are not limited to the above two kinds ofconditions and may include a condition where a plurality of ultrasonicwaves for attenuation quantification having different frequencies aretransmitted to one scanning line. Alternatively, the transmissionconditions may include a condition where two ultrasonic waves forattenuation quantification whose phases are inverted are transmitted toone scanning line. The transmission center frequency in the transmissionconditions is higher than the transmission center frequency of anultrasonic wave for B-mode, for example. The bandwidth in thetransmission conditions (hereinafter referred to as a narrow band) isnarrower than the bandwidth of the ultrasonic wave for B-mode.

In response to the attenuation quantification start instruction from anoperator via the input apparatus 5, the attenuation quantificationconditions are read from the storage circuitry 25 to the processingcircuitry 29. The ultrasonic transmitting circuitry 11 is controlled bythe processing circuitry 29 in accordance with the transmissionconditions in the attenuation quantification conditions. For example,the ultrasonic transmitting circuitry 11 transmits a plurality ofultrasonic waves having different frequencies to the subject P via theultrasonic probe 3 in accordance with the transmission conditions inultrasonic scanning. The ultrasonic transmitting circuitry 11 transmitsan ultrasonic wave in the band narrower than the frequency band in theultrasonic transmission concerning the B-mode to the subject P via theultrasonic probe 3 in accordance with the transmission conditions inultrasonic scanning.

The ultrasonic receiving circuitry 13 has a preamplifier 131, an analogto digital (hereinafter referred to as A/D) converter (not shown),reception delay circuitry 133, and an adder 135. The ultrasonicreceiving circuitry 13 is an example of an ultrasonic reception unit andmay have a processor. The preamplifier 131 amplifies an echo signal fromthe subject P received via the ultrasonic probe 3 for each channel. TheA/D converter converts the received echo signal having been amplifiedinto a digital signal. An analog gain is given as STC (sensitive timecontrol) or TGC (time gain control) to an analog signal before A/Dconversion.

The reception delay circuitry 133 gives the received echo signal havingbeen converted into a digital signal a delay time (hereinafter referredto as a reception delay time) necessary to determine receptiondirectivities. The reception delay circuitry 133 is a digital beamformer, for example. A digital gain is given as STC or TGC to a digitalsignal output from the reception delay circuitry 133. The storagecircuitry 25 to be described later stores the reception direction of anecho signal or the reception delay time concerning the receptiondirection (hereinafter referred to as a reception delay pattern). Theprocessing circuitry 29 refers to the reception delay pattern stored inthe storage circuitry 25 as when ultrasonic waves are transmitted.

Due to attenuation of an ultrasonic wave in a subject, a signal due to areflected wave becomes faint as it approaches a depth in the subject.Thus, the analog gain and the digital gain are gains which furtheramplify the amplitude of a signal due to an ultrasonic wave reflected inthe depth in the subject in order to compensate this attenuation.

The adder 135 adds a plurality of echo signals to which the delay timesare given. With this addition processing, the ultrasonic receivingcircuitry 13 generates a reception signal in which a reflectioncomponent from a direction corresponding to the reception directivity isenhanced. The transmission directivity and the reception directivitydetermine the comprehensive directivity of ultrasonictransmission/reception. This comprehensive directivity determines anultrasonic beam (so-called “ultrasonic scanning line”).

The ultrasonic receiving circuitry 13 receives an ultrasonic wave forattenuation quantification in accordance with the reception conditionsin the attenuation quantification conditions. The reception centerfrequency in the reception conditions is a frequency being substantiallythe same as the transmission center frequency of an ultrasonic wave forattenuation quantification and is constant without changing with respectto a depth direction in a scanned region. The reception bandwidth in thereception conditions is a bandwidth being substantially the same as thenarrow band. The ultrasonic receiving circuitry 13 is controlled by theprocessing circuitry 29 in accordance with the reception conditions inthe attenuation quantification conditions.

Specifically, the ultrasonic receiving circuitry 13 receives a reflectedwave of an ultrasonic wave for attenuation quantification transmitted tothe subject P in accordance with the reception conditions in response tothe generation of the B-mode data to be described later corresponding toone frame. The ultrasonic receiving circuitry 13 generates receptiondata for attenuation quantification based on the reception of thereflected wave of the ultrasonic wave for attenuation quantification.The ultrasonic transmitting circuitry 11 outputs the reception data forattenuation quantification to the B-mode processing circuitry 15. Theultrasonic transmitting circuitry 11 may output the reception data forattenuation quantification to the processing circuitry 29 and thestorage circuitry 25.

The B-mode processing circuitry 15 includes an envelope detector and alogarithmic converter (neither of which is shown). The B-mode processingcircuitry 15 is an example of a B-mode processing unit and has aprocessor. The envelope detector executes envelope detection of thereception signal output from the ultrasonic receiving circuitry 13. Theenvelope detector outputs the envelope-detected signal to thelogarithmic converter to be described later. The logarithmic converterrelatively enhances a weak signal by logarithmically converting theenvelope-detected signal. The B-mode processing circuitry 15 generates asignal value (B-mode data) for each depth on each scanning line and ineach ultrasonic transmission/reception based on the signal enhanced bythe logarithmic converter.

The B-mode data corresponds to data in which the strength of a signaloutput from the logarithmic converter is expressed as a luminance. Anoutput from the B-mode processing circuitry 15 is output to the imagegenerating circuitry 19. The output from the B-mode processing circuitry15 is displayed as a B-mode image, in which strength of a reflected waveis expressed as a luminance, on the monitor 7. The B-mode processingcircuitry 15 generates B-mode data for attenuation quantification inaccordance with the above processing procedure based on the receptiondata for attenuation quantification. The B-mode processing circuitry 15outputs the B-mode data for attenuation quantification to the processingcircuitry 29 and the storage circuitry 25.

When the ultrasonic probe 3 is a mechanical four-dimensional probe ortwo-dimensional array probe, the B-mode processing circuitry 15 maygenerate three-dimensional B-mode data comprising a plurality of signalvalues respectively correspondingly arranged in the azimuth direction,elevation direction, and depth direction (range direction) in a scannedregion. The range direction is the depth direction on a scanning line.The azimuth direction is, for example, an electronic scanning directionalong the array direction of piezoelectric transducers in aone-dimensional array. The elevation direction is, for example, amechanical swinging direction of the one-dimensional array.

The three-dimensional B-mode data may be data obtained by arranging aplurality of pixel values, a plurality of luminance values, or the likein the azimuth direction, the elevation direction, and the rangedirection, respectively, along scanning lines. The three-dimensionalB-mode data may be data concerning ROI previously set in a scannedregion. The B-mode processing circuitry 15 may generate volume datainstead of the three-dimensional B-mode data. Hereinafter, data itemsgenerated by the B-mode processing circuitry 15 will be collectivelyreferred to as B-mode data.

The Doppler processing circuitry 17 frequency-analyzes velocityinformation from the echo signal received from the ultrasonic receivingcircuitry 13. The Doppler processing circuitry 17 is an example of aDoppler processing unit and has a processor. The Doppler processingcircuitry 17 extracts a blood flow, tissue, and contrast medium echocomponent by the Doppler effect from the echo signal received from theultrasonic receiving circuitry 13. The Doppler processing circuitry 17obtains blood flow information such as a mean velocity, variance, andpower at multiple points on a scanning line. The Doppler processingcircuitry 17 outputs the obtained blood flow information to the imagegenerating circuitry 19. The output from the Doppler processingcircuitry 17 is color-displayed as a Doppler waveform image, a meanvelocity image, a variance image, a power image, or a combination imagethereof on the monitor 7.

The Doppler processing circuitry 17 includes a mixer, a low pass filter(hereinafter referred to as an LPF), and velocity/variance/powercomputation circuitry (none of which are shown). The mixer multipliesthe reception signal output from the ultrasonic receiving circuitry 13by a reference signal having a frequency f₀ equal to the transmissionfrequency. This multiplication obtains a signal having a component witha Doppler shift frequency f_(d) and a signal having a frequencycomponent of (2f₀+f_(d)). The LPF removes a signal of a high-frequencycomponent (2f₀+f_(d)) from signals having two types of frequencycomponents from the mixer. The Doppler processing circuitry 17 generatesa Doppler signal having the component with the Doppler shift frequencyf_(d) by removing the signal of the high-frequency component(2f₀+f_(d)).

The Doppler processing circuitry 17 may use a quadrature detectionscheme to generate Doppler signals. In this case, a reception signal (RFsignal) is subjected to quadrature detection to be converted into an IQsignal. A Doppler processing unit 142 generates a Doppler signal havingthe component with the Doppler shift frequency f_(d) by applying complexFourier transform to the IQ signal. Doppler signals are, for example,Doppler components based on a blood flow, tissue, and contrast medium.

The velocity/variance/power computation circuitry includes an MTI(Moving Target Indicator) filter, an LPF filter, and an autocorrelationcomputation unit (none of which are shown). This circuitry may include across-correlation computation unit instead of an autocorrelationcomputation unit. The MTI filter removes a Doppler component (a cluttercomponent) caused by the respiratory movement or pulsatory movement ofan organ or the like from a generated Doppler signal. The MTI filter isused to extract a Doppler component (hereinafter referred to as a bloodflow Doppler component) concerning a blood flow from a Doppler signal.The LPF is used to extract a Doppler component (hereinafter referred toas a tissue Doppler component) concerning the movement of the tissuefrom a Doppler signal.

The autocorrelation computation unit calculates autocorrelation valuesconcerning a blood flow Doppler signal and a tissue Doppler component.The autocorrelation computation unit calculates the mean velocity valuesof the blood flow and the tissue, variances, the reflection intensities(powers) of Doppler signals, and the like based on the calculatedautocorrelation values. The velocity/variance/power computationcircuitry generates color Doppler data at the respective positions in apredetermined region based on the mean velocity values of the blood flowand the tissue, the variances, the reflection intensities of the Dopplersignals, and the like based on a plurality of Doppler signals.Hereinafter, Doppler signals and color Doppler data will be collectivelyreferred to as Doppler data.

The image generating circuitry 19 includes a digital scan converter(hereinafter referred to as a DSC) (not shown). The image generatingcircuitry 19 is an example of an image generating unit and has aprocessor. The image generating circuitry 19 executes coordinatetransformation processing (resampling) for the DSC. The coordinatetransformation processing is to transform, for example, a scanning linesignal string for ultrasonic scanning, which is formed from B-mode dataand Doppler data, into a scanning line signal string in a general videoformat typified by a TV format.

The image generating circuitry 19 generates an ultrasonic image as adisplay image by executing coordinate transformation processing.Specifically, the image generating circuitry 19 generates a B-mode imagebased on B-mode data. The image generating circuitry 19 generates anattenuation B-mode image based on B-mode data for attenuationquantification. The B-mode image and the attenuation B-mode image havepixel values (luminance value) reflecting characteristics of anultrasonic probe such as convergence of sonic waves, sound fieldcharacteristics of an ultrasonic beam (for example, atransmission/reception beam), and the like. For example, in the B-modeimage, the luminance near the focus of ultrasonic waves in a scannedregion is relatively higher than that in a non-focus portion.

The image generating circuitry 19 generates a Doppler image such as amean velocity image, a variance image, and a power image based onDoppler data. The image generating circuitry 19 further generates anattenuation quantification image showing the ultrasonic attenuationamount at each position in a partial region in a scanned region, basedon the analysis results analyzed by the analysis function 299.

The image memory 21 stores data (hereinafter referred to as image data)corresponding to a generated ultrasonic mage (a B-mode image, meanvelocity image, variance image, power image, or attenuationquantification image). The image data stored in the image memory 21 isread out in accordance with an instruction issued by an operator via theinput apparatus 5. The image memory 21 is, for example, a memory whichstores ultrasonic images corresponding to a plurality of framesimmediately before freezing. When the images stored in this cine memoryare continuously displayed (cine-displayed) at a predetermined framerate, a moving ultrasonic image is displayed on the monitor 7.

The image memory 21 is realized by, for example, an integrated circuitmemory (such as a random access memory (RAM) and a read-only memory(ROM)). The image memory 21 may be realized by any storage apparatus inaddition to the above integrated circuit memories.

The image compositing circuitry 23 composites character information ofvarious parameters, scale marks, and the like on an ultrasonic image.The image compositing circuitry 23 is an example of an image compositingunit and has a processor. The image compositing circuitry 23 outputs thecomposited ultrasonic image to the monitor 7 to be described later. Theimage compositing circuitry 23 generates an attenuation superimpositionimage formed by positioning and superimposing an attenuationquantification image on a B-mode image. The image compositing circuitry23 outputs the generated attenuation superimposition image to themonitor 7.

The storage circuitry 25 is a storage apparatus such as an HDD (harddisk drive), SSD (solid state drive), or an integrated circuit memory(such as RAM or ROM) storing various kinds of information. The storagecircuitry 25 corresponds to a storage unit. The storage circuitry 25 maybe realized by a drive apparatus which reads and writes various kinds ofinformation from and in a CD-ROM drive, a DVD drive, or the like.Further, the storage circuitry 25 may be realized by a drive apparatuswhich reads and writes various kinds of information from and in portablestorage media such as magnetic disks (such as Floppy (trademark) disks),optical disks (such as CD-ROMs, DVDs, and MOs), and semiconductormemories.

The storage circuitry 25 stores a plurality of reception delay patternsand a plurality of transmission delay patterns with different focusdepths. The storage circuitry 25 stores a control program for theultrasonic diagnosis apparatus 1, a diagnosis protocol, and a medicalanalysis program to be described later. The storage circuitry 25 storesvarious data groups such as ultrasonic transmission/reception conditionsand diagnosis information (such as patient ID and doctor's opinions).The storage circuitry 25 stores reception signals generated by theultrasonic receiving circuitry 13, the B-mode data generated by theB-mode processing circuitry 15, the Doppler data generated by theDoppler processing circuitry 17, and the analysis data showing theanalysis results obtained by the analysis function 299.

Further, the storage circuitry 25 stores a program (hereinafter referredto as a structure estimation program) concerning the sizes and settingpositions of a plurality of regions set in a scanned region (attenuationB-mode image) concerning collection of B-mode data for attenuationquantification and execution of a structure estimation function. Thestorage circuitry 25 stores a threshold (hereinafter referred to as astructure determination threshold) referred in the structure estimationfunction. The storage circuitry 25 stores reverse correction data usedin the gain reverse correction function 295, sound field characteristiccorrection data used in the sound field characteristic correctionfunction 297, a program (hereinafter referred to as a tissuecharacterization analysis program) concerning execution of the tissuecharacterization analysis function, and so on. Hereinafter, thestructure estimation program and the tissue characterization analysisprogram will be collectively referred to as a medical analysis program.

The storage circuitry 25 may store a correspondence table (hereinafterreferred to as a reverse correction correspondence table) instead of thereverse correction data. The storage circuitry 25 may store acorrespondence table (hereinafter referred to as a sound fieldcharacteristic correction correspondence table) instead of the soundfield characteristic correction data.

The reverse correction data is data used for cancelling an analog gainand a digital gain applied to data (reception signal or reception data)obtained by ultrasonic scanning by the STC or the TGC. Specifically, thereverse correction data is data showing a response in a depth directionof a gain applied to the data obtained by ultrasonic scanning. Namely,when the reverse correction data is applied to the B-mode data, the gaincorrected B-mode data is converted into the B-mode data before gaincorrection.

The reverse correction correspondence table is a correspondence tableused for cancelling gain correction according to the STC or the TGC.Specifically, the reverse correction correspondence table is acorrespondence table showing the response in the depth direction of thegain applied to the data obtained by ultrasonic scanning and acorrespondence table used for converting the B-mode data after gaincorrection into the B-mode data before gain correction.

The sound field characteristic correction data is data used forcancelling dependency of the sound field characteristics in the B-modedata before gain correction. Namely, when the sound field characteristiccorrection data is applied to the B-mode data, the B-mode data dependingon the sound field characteristics is converted into the B-mode data notdepending on the sound field characteristics. The sound fieldcharacteristic correction correspondence table is a correspondence tableused for cancelling the dependency of the sound field characteristics inthe B-mode data. Specifically, the sound field characteristic correctioncorrespondence table is a correspondence table used for converting theB-mode data depending on the sound field characteristics into the B-modedata not depending on the sound field characteristics.

The sound field characteristic correction data and the sound fieldcharacteristic correction correspondence table correspond to, forexample, a distribution of pixel values (or luminance values) in thedepth direction obtained when ultrasonic scanning is executed withrespect to an object in which an ultrasonic wave is not attenuated andwhich has uniform scatterers. The sound field characteristic correctiondata and the sound field characteristic correction correspondence tableare previously generated based on actual measured data obtained byexecuting ultrasonic scanning with respect to a uniform phantom in whichan ultrasonic wave is not attenuated.

The sound field characteristic correction data and the sound fieldcharacteristic correction correspondence table may be generated bydifferentiating an ultrasonic attenuation due to a phantom, having aconstant attenuation with respect to an ultrasonic wave, from actualmeasured data actually measured by ultrasonic scanning with respect tothis phantom. The sound field characteristic correction data and thesound field characteristic correction correspondence table may begenerated by other means such as simulation.

The storage circuitry 25 stores various images such as a B-mode image, amean velocity image, a variance image, a power image, an attenuationquantification image, and an attenuation superimposition image. Thestorage circuitry 25 stores a plurality of color phases corresponding toa plurality of attenuation constants to be described later. The storagecircuitry 25 stores a predetermined opacity or transparency concerningan attenuation quantification image. The storage circuitry 25 stores acolor phase corresponding to a value of a variance ratio to be describedlater. The storage circuitry 25 may include the above-described imagememory 21. When CFAR (Contrast False Alarm Rate) processing is executedas the structure estimation function, the storage circuitry 25 may storea program concerning the CFAR processing.

The interface circuitry 27 is an interface associated with the inputapparatus 5, an operation panel (not shown), a network, an externalstorage apparatus (not shown), and a biological signal measurer (notshown). The data such as ultrasonic images, analysis results, and thelike obtained by the apparatus body 9 can be transferred to anotherapparatus through the interface circuitry 27 and the network. Theinterface circuitry 27 can download a medical image concerning a subjectobtained by another medical image diagnosis apparatus (not shown)through the network. The interface circuitry 27 corresponds to aninterface unit and may have a processor.

The processing circuitry 29 has a function as an information processingapparatus (calculator) and is control means (processor) controllingoperation of the apparatus body 9 of the ultrasonic diagnosis apparatus1. The processing circuitry 29 reads out control programs for executingimage generation/display and the like from the storage circuitry 25 andexecutes computation, control, and the like associated with each type ofprocessing. The processing circuitry 29 corresponds to a control unit.

The processing circuitry 29 reads out the attenuation quantificationconditions from the storage circuitry 25 in response to the attenuationquantification start instruction. The processing circuitry 29 controlsthe ultrasonic transmitting circuitry 11 and the ultrasonic receivingcircuitry 13 in accordance with the read-out attenuation quantificationconditions. Specifically, the processing circuitry 29 controls theultrasonic transmitting circuitry 11 in accordance with the read-outtransmission conditions. According to this constitution, the ultrasonictransmitting circuitry 11 transmits an ultrasonic wave for attenuationquantification to the subject P after generation of the B-mode datacorresponding to one frame. The processing circuitry 29 controls theultrasonic receiving circuitry 13 in accordance with the read-outreception conditions. According to this constitution, the ultrasonicreceiving circuitry 13 receives a reflected wave of an ultrasonic wavefor attenuation quantification, transmitted to the subject P, inaccordance with the reception conditions.

In the present embodiment, the respective processing functions performedby the setting function 291, the estimation function 293, the gainreverse correction function 295, the sound field characteristiccorrection function 297, and the analysis function 299 are stored in thestorage circuitry 25 in the form of computer-executable programs. Theprocessing circuitry 29 is a processor which reads out the programscorresponding to those functions from the storage circuitry 25 toexecute the programs and thus to achieve the functions corresponding tothe respective programs. In other words, the processing circuitry 29 ina state of reading out each program has each function shown in theprocessing circuitry 29 of FIG. 1.

There may be a case where each of the above functions is constituted asa program, and each program is executed by one processing circuit, orthere may be case where the estimation function is mounted on adedicated independent program execution circuit. The setting function291, the estimation function 293, the gain reverse correction function295, the sound field characteristic correction function 297, and theanalysis function 299 of the processing circuitry 29 are respectivelyexamples of a setting unit, an estimation unit, a gain reversecorrection unit, a sound field characteristic correction unit, and ananalysis unit. In this case, a processor which achieves the structureestimation function may function as a structure estimation unit.Further, a processor which achieves the tissue characterization analysisfunction may function as a tissue characterization analysis unit.

The term “processor” used in the above description means, for example,CPU, GPU (Graphical Processing Unit), or a circuit such as anapplication specific integrated circuit (ASIC), a programmable logicdevice (for example, a simple programmable logic device (SPLD)), acomplex programmable logic device (CPLD), and a field programmable gatearray (FPGA).

The processor reads out and executes a program stored in storagecircuitry 25 and thereby achieves the function. There may be constitutedsuch that the program is directly incorporated in circuitry of theprocessor instead of being stored in the storage circuitry 25. In thiscase, the processor reads out and executes the program incorporated inthe circuitry and thereby achieves the function. Other circuitry such asthe ultrasonic transmitting circuitry 11, the ultrasonic receivingcircuitry 13, the B-mode processing circuitry 15, the Doppler processingcircuitry 17, the image generating circuitry 19, the image compositingcircuitry 23, and the interface circuitry 27 are similarly constitutedof electronic circuits of the above processor or the like.

The processing circuitry 29 reads out the medical analysis program fromthe storage circuitry 25 in response to the attenuation quantificationstart instruction. The processing circuitry 29 executes the read-outmedical analysis program and thereby achieves the structure estimationfunction and the tissue characterization analysis function.Specifically, the processing circuitry 29 reads out the structureestimation program and the tissue characterization analysis program fromthe storage circuitry 25. The processing circuitry 29 executes theread-out structure estimation program and thereby estimates a positionof a structure in a subject based on the B-mode data for attenuationquantification obtained by ultrasonic scanning using an ultrasonic wavefor attenuation quantification.

For example, the processing circuitry 29 executes the read-out tissuecharacterization analysis program in response to the estimation of theposition of the structure and thereby analyzes tissue characterizationin a scanned region corresponding to the B-mode data for attenuationquantification. Hereinafter, various functions concerning the estimationof a position of a structure in a subject and various functionsconcerning the analysis of the tissue characterization will bespecifically described.

In the following description, although the setting function 291, theestimation function 293, the gain reverse correction function 295, thesound field characteristic correction function 297, the analysisfunction 299, and the like are executed in the single processingcircuitry 29, a processing circuitry is constituted by combining aplurality of independent processors, and each processor executes aprogram, whereby various functions may be achieved. The setting function291, the estimation function 293, the gain reverse correction function295, the sound field characteristic correction function 297, theanalysis function 299, and the like may be achieved by differentprocessing circuitry or processors.

(Structure Estimation Function)

The structure estimation function include a function of evaluatingununiformity at a plurality of positions in a subject based on theB-mode data for attenuation quantification obtained by ultrasonicscanning with respect to the subject P and thereby estimating a positionof a structure. As the structure estimation function, there are variousmethods of estimating a structure. Hereinafter, as one example of such amethod, there will be described a method using a mean value of aplurality of pixel values (or luminance values) respectivelycorresponding to a plurality of pixels included in each of a pluralityof regions set in an attenuation B-mode image and variance values.

This method generally uses the fact that in a region having uniformscatterers such as the parenchyma of the liver, frequency distribution(histogram) of the B-mode data for attenuation quantification exhibitsRayleigh distribution. In the region having uniform scatterers, when thefrequency distribution of the B-mode data for attenuation quantificationfollows the Rayleigh distribution, a mean value (μ) and a variance value(σ²) due to a plurality of pixel values in this region have thefollowing relationship.σ²=(4/π−1)×μ²  (1)

When a structure is included in a region concerning calculation of themean value and the variance value, since scatterers are nonuniform, thevariance value of the frequency distribution of the B-mode data forattenuation quantification is larger than the variance value calculatedaccording to the Rayleigh distribution. In addition, the moresignificantly different characteristics of a structure from thesurroundings (for example when the region of the structure correspondsto a calcified region), the larger the variance value. Thus, a presenceof a structure in each pixel representing a region can be determined bycalculating a variance value in each of a plurality of regions set in ascanned region.

However, since the larger the pixel value, the larger the variancevalue, the presence of a structure, that is, occurrence of deviationfrom the Rayleigh distribution obtained in the case of uniformscatterers cannot be determined by simply calculating the variance valueitself. Thus, in this embodiment, the Rayleigh distribution having amean value being the same as a mean value of pixel values in a setregion is assumed with respect to the set region. Based on thisassumption, there is calculated a ratio (hereinafter referred to as avariance ratio R_(σ)) of the variance value σ² of the pixel value in theset region with respect to a variance value {(4/π−1)×μ²} calculatedusing the mean value of the pixel values in the set region and theformula (1). Specifically, the variance ratio R_(τ) is represented bythe following formula.R _(σ)=σ²/{(4/π−1)×μ²}  (2)

The molecule (σ²) at the right side of the formula (2) is an actuallymeasured variance value calculated from a plurality of pixel valuesrespectively corresponding to a plurality of pixels included in the setregion. The denominator {(4/π−1)×μ²} at the right side of the formula(2) is a variance value in a case where it is assumed that with the useof a mean value μ, calculated from pixel values of variancesrespectively corresponding to a plurality of pixels included in the setregion, and the formula (1), the pixel values in the set region form theRayleigh distribution.

When the variance ratio R_(σ) is close to 1, the distribution of thepixel values in the set region can be regarded as the Rayleighdistribution. When the variance ratio R_(τ) is more than 1, it isestimated that the distribution of the pixel values included in the setregion deviates from the Rayleigh distribution, and the set regionincludes a structure deviated from uniform scatterers. Namely, thevariance ratio R_(σ) corresponds to an index of determination of thepresence of a structure in the set region.

The processing circuitry 29 achieving the setting function 291 sets aplurality of regions in a scanned region (attenuation B-mode image) inwhich the B-mode data for attenuation quantification is collected, thatis, a scanning region in ultrasonic scanning using ultrasonic waves forattenuation quantification. The set regions have predetermined sizeswith each pixel in an attenuation B-mode image as the center(hereinafter referred to as a center pixel) or the center of thegravity. The size of the region set in the attenuation B-mode image maybe suitably changed by an instruction from an operator via the inputapparatus 5. The processing circuitry 29 may sweep one region for eachwidth of a predetermined pixel and thereby set a plurality of regions inthe attenuation B-mode image.

The processing circuitry 29 achieving the estimation function 293estimates a position of a structure based on a pixel value (or luminancevalue) corresponding to each of a plurality of pixels included in eachof a plurality of set regions. At this time, the pixel value correspondsto the pixel value in the B-mode data for attenuation quantification.The estimation function 293 may use a pixel value in usual B-mode data.Specifically, the processing circuitry 29 calculates a mean value ofpixel values (or luminance values) and a variance value in each of aplurality of regions. The processing circuitry 29 calculates thevariance ratio R_(σ) based on the mean value and the variance value. Thecalculated variance ratio R_(σ) may be stored in the storage circuitry25. The variance ratio R_(τ) may be displayed on the monitor 7 whilebeing superimposed on a B-mode image in a scanned region, being the sameas the scanned region concerning the variance ratio R_(σ), in colorphase corresponding to the value of the variance ratio R_(σ).

FIG. 2 is a B-mode image on which the variance ratio R_(σ) is to besuperimposed in the color phase corresponding to the value of thevariance ratio R_(σ). The B-mode image shown in FIG. 2 shows a crosssection of the liver of the subject P. FIG. 3 is a view showing anexample of a variance ratio superimposition image in which the varianceratio R_(τ) is superimposed on the B-mode image of FIG. 2 in the samescanned region concerning calculation of the variance ratio R_(τ) in thecolor phase corresponding to the value of the variance ratio R_(τ). Adifference in hatching in FIG. 3 corresponds to a difference in colorphase. Although FIG. 3 shows three types of color phases of the varianceratio R_(τ) for ease of illustration of the variance ratiosuperimposition image, a substantially continuous color phase isactually displayed on the monitor 7, together with a legend showing thecolor phase of the variance ratio R_(τ).

The hatching LR in FIG. 3 shows a region where the variance ratio R_(τ)is large. As shown in FIG. 3, in a region of a structure, such as bloodvessels, an abdominal wall, or diaphragm, or a region around thestructure, the variance ratio R_(σ) is large as compared with theparenchyma of the liver having a uniform speckle. Namely, as seen inFIG. 3, in the region of the structure and the region around thestructure, scattering characteristics of ultrasonic waves are ununiform.Thus, the region of the structure and the region around the structureare not appropriate as an analysis target of the ultrasonic attenuationamount.

The processing circuitry 29 makes the calculated variance ratio R_(τ)correspond to a position representing the region set by the settingfunction 291, for example, a position of the center pixel. Theprocessing circuitry 29 reads out the structure determination thresholdfrom the storage circuitry 25. The structure determination threshold isa numerical value being not less than 1. The structure determinationthreshold may be suitably changed by an instruction from an operator viathe input apparatus 5. The processing circuitry 29 compares the read-outstructure determination threshold and the variance ratio R_(σ). Theprocessing circuitry 29 estimates the variance ratio R_(τ) being largerthan the structure determination threshold as a position of a structure.

The processing circuitry 29 achieving the estimation function 293 mayoutput, to the storage circuitry 25, the structure position estimated ina scanned region corresponding to an attenuation B-mode image, that is,the region of the structure. The estimated structure position is used inthe tissue characterization analysis function to be described later. Theestimated region of the structure corresponds to a region shown by thehatching LR, as shown in FIG. 3, for example.

The method of estimating a structure with the use of a reception signaland the B-mode data for attenuation quantification is not limited to theabove method. For example, the structure estimation function may use apresumptive signal (or image) extraction technique referred to as CFARprocessing. The term “CFAR processing” is used in the field of radars.In this embodiment, for convenience, the term “CFAR” is used forspecific description according to its relevance. However, the term “CFARprocessing” is irrespective of a method used in the field of radars or amethod strictly using a statistical quantity.

The CFAR processing is executed by the following procedures (1) to (3),for example.

(1) The processing circuitry 29 achieving the setting function 291 setsa region having neighboring pixels near a target pixel Pi for each ofthe target pixels Pi in an attenuation B-mode image. The region set asthe neighboring pixels by the processing circuitry 29 is provided in across shape in the attenuation B-mode image. However, arrangement of theneighboring pixels in the set region is not limited to the cross shape,and for example when the time required for arithmetic processing doesnot cause a problem, there may be a region having any size except foreight pixels adjacent to a target pixel.

The processing circuitry 29 achieving the estimation function 293calculates a luminance mean value (or pixel mean value) in the setregion. At this time, in order to prevent a luminance value (or pixelvalue) of a target pixel from affecting a mean value, the processingcircuitry 29 may calculate the luminance mean value such that the targetpixel Pi itself is not included in the calculation.

(2) Next, the processing circuitry 29 subtracts the mean value from thepixel value of the target pixel Pi. The processing circuitry 29 definesthe subtraction value as an arithmetic result Ki with respect to aposition of the target pixel Pi and allows the storage circuitry 25 tostore the arithmetic result Ki. The processing circuitry 29 executes thearithmetic processing with respect to all the target pixels Pi.

(3) The processing circuitry 29 reads out a previously set threshold Tfrom the storage circuitry 25. In this case, the threshold T correspondsto the structure determination threshold and is generally a valuedifferent from the structure determination threshold corresponding tothe variance ratio R_(σ). The processing circuitry 29 compares thearithmetic result Ki and the threshold T. When Ki≥T, the target pixel Piis displayed using original luminance (extraction of a structure). Onthe other hand, when Ki<T, the luminance value of the target pixel Pi istaken to be 0 and is thus not displayed (removal of a structure). TheCFAR processing concerning the image can be executed by executing theabove processing with respect to all the target pixels Pi.

In the determination in (3), it may be configured such that when Ki≥T,the target pixel Pi is displayed while the luminance is taken to be Ki,and when Ki<T, the luminance value of the target pixel Pi is taken to be0 and is thus not displayed.

More simply, the structure estimation function may estimate a positionof a structure by comparing a mean value of luminance values (or pixelvalues) in a plurality of regions set in a usual B-mode image, avariance value, a standard deviation, and the like and thresholds usedfor structure determination corresponding to the respective values.

(Tissue Characterization Analysis Function)

The tissue characterization analysis function is executed by theprocessing circuitry 29 in accordance with the tissue characterizationanalysis program. Specifically, the tissue characterization analysisfunction analyzes tissue characterization with respect to a plurality ofpositions except for a position of a structure estimated in anattenuation B-mode image based on B-mode data for attenuationquantification. The tissue characterization analysis function has thegain reverse correction function 295, the sound field characteristiccorrection function 297, the analysis function 299, and a displayfunction (not shown). Hereinafter, each function in the tissuecharacterization analysis function will be described in detail. Thetissue characterization is, for example, a feature quantity concerningan attenuation amount showing a degree of attenuation of an ultrasonicwave for attenuation quantification propagating inside a subject.

The tissue characterization is not limited to the attenuation amount andmay be an amount showing characterization of a tissue to be diagnosed,such as modulus of elasticity (Young's modulus), viscosity, anddistortion. In this case, the tissue characterization is obtained by anultrasonic elastography method, for example. The analysis function 299has various analysis functions concerning a static or dynamicelastography method. In this case, the processing circuitry 29 achievingthe analysis function 299 calculates as the tissue characterization anindex value (viscosity parameter or elasticity parameter) concerning atleast one of viscosity and elasticity of a tissue in a subject.

In a typified ultrasonic elastography method, a tissue in a subject ispressed/released from a surface of the body by the ultrasonic probe 3,whereby relative hardness of the tissue in the subject is visualizedbased on a magnitude of distortion at each point in a cross sectionobserved during pressing/releasing.

In another typified ultrasonic elastography method, displacement(distortion) of a tissue at each point in a cross section is observedwith the lapse of time by applying acoustic radiant power or mechanicalvibration to a tissue in the subject P from the body surface of thesubject P. Specifically, the dynamic ultrasonic elastography method is amethod of obtaining the propagation velocity of shear waves generated byacoustic radiant power or mechanical vibration and thereby obtaining themodulus of elasticity, viscosity, and the like of the tissue to bediagnosed. Ultrasonic waves transmitted and received by the static ordynamic ultrasonic elastography method correspond to ultrasonic wavesfor attenuation quantification. In this case, as data used in thestructure estimation function, B-mode data concerning generation of aB-mode image is used. An image (such as an elasticity image, a viscosityimage, and a distortion image) generated by the ultrasonic elastographymethod corresponds to an attenuation quantification image.

Hereinafter, the tissue characterization analysis function will bedescribed as the function of calculating the attenuation amount as thetissue characterization. Prior to the execution of the gain reversecorrection function 295, the processing circuitry 29 estimates data(hereinafter referred to as partial data for attenuation quantification)corresponding to a plurality of positions except for a position of astructure estimated in a scanned region corresponding to an attenuationB-mode image in B-mode data for attenuation quantification.

The processing circuitry 29 achieving the gain reverse correctionfunction 295 reads out reverse correction data from the storagecircuitry 25. The processing circuitry 29 subtracts the reversecorrection data from the partial data for attenuation quantificationcorresponding to a plurality of positions except for a position of astructure estimated in a scanned region. According to this constitution,the processing circuitry 29 generates the partial data for attenuationquantification, which is not subjected to gain correction. Theprocessing circuitry 29 may read out the reverse correctioncorrespondence table from the storage circuitry 25. In this case, theprocessing circuitry 29 converts the partial data for attenuationquantification into the partial data for attenuation quantificationbefore gain correction in accordance with the reverse correctioncorrespondence table. Namely, the gain reverse correction function 295cancels gain correction with respect to the partial data for attenuationquantification.

By virtue of the gain reverse correction function 295, the processingcircuitry 29 restores reception data at the time when the ultrasonicprobe 3 has received a reflected wave of an ultrasonic wave forattenuation quantification, that is, the pure strength of adepth-directional ultrasonic signal along the depth direction. Ifuncorrected partial data for attenuation quantification (raw data) canbe output from the ultrasonic receiving circuitry 13, the gain reversecorrection function 295 is not required.

The processing circuitry 29 achieving the sound field characteristiccorrection function 297 reads out sound field characteristic correctiondata from the storage circuitry 25. The processing circuitry 29subtracts the sound field characteristic correction data from thepartial data for attenuation quantification before gain correction.Consequently, the processing circuitry 29 generates the partial data forattenuation quantification (hereinafter referred to as attenuationdata), which is not subjected to gain correction and does not depend onthe sound field characteristics. The processing circuitry 29 may readout the sound field characteristic correction correspondence table fromthe storage circuitry 25. In this case, the processing circuitry 29converts the partial data for attenuation quantification before gaincorrection into the attenuation data in accordance with the sound fieldcharacteristic correction correspondence table. Namely, the processingcircuitry 29 cancels the dependency on the sound field characteristicsin the partial data for attenuation quantification before gaincorrection, based on the sound field characteristics in ultrasonicscanning.

By virtue of the sound field characteristic correction function 297, theprocessing circuitry 29 eliminates a variation of a pixel value (orluminance value) specific to the shape of an ultrasonic beam and theshape of the ultrasonic probe 3 from B-mode data for attenuationquantification before gain correction. By virtue of this elimination,the processing circuitry 29 generates attenuation rata having a pixelvalue (or luminance value) reflecting a degree of pure attenuation of anultrasonic wave due to a tissue in a subject. The attenuation datacorresponds to correction data corrected by the gain reverse correctionfunction 295 and the sound field characteristic correction function 297.

The processing circuitry 29 executing the analysis function 299 analyzesthe tissue characterization at a plurality of positions in a subjectexcept for an estimated structure position (the positions will behereinafter referred to as a non-structure region) based on theattenuation data obtained by ultrasonic scanning with respect to thesubject P. Namely, the processing circuitry 29 achieving the analysisfunction 299 calculates the attenuation amount of an ultrasonic wave forattenuation quantification propagating inside a subject.

Specifically, the processing circuitry 29 calculates a differentialvalue along a depth direction in a pixel value (or luminance value) inthe non-structure region in attenuation data. The differential valuecorresponds to, for example, a value obtained by dividing a differencevalue between pixel values of two pixels adjacent along the depthdirection by an interval (distance) between the two pixels in each of aplurality of pixels in the non-structure region.

Subsequently, the processing circuitry 29 multiplies the calculateddifferential value by ½ while considering two ways of ultrasonic waves.Consequently, the processing circuitry 29 calculates the ultrasonicattenuation amount (dB/cm) concerning the transmission center frequencyof an ultrasonic wave for attenuation quantification with respect to aplurality of pixels (positions) included in the non-structure region.Further, the processing circuitry 29 divides the calculated attenuationamount by the transmission center frequency of an ultrasonic wave forattenuation quantification. By virtue of the division, the processingcircuitry 29 calculates attenuation constants (dB/cm/Hz) at a pluralityof pixels (positions) included in the non-structure region.

The attenuation constant does not depend on the transmission centerfrequency of an ultrasonic wave for attenuation quantification. Further,the attenuation constant is substantially constant for each of aplurality of pixels (positions) included in the non-structure region.The attenuation constant is a numerical value representingcharacterization of a tissue to be diagnosed. By virtue of the abovevarious calculations, the processing circuitry 29 generates analysisdata (hereinafter referred to as attenuation constant data) showingattenuation constants at a plurality of positions included in thenon-structure region. The processing circuitry 29 outputs theattenuation constant data to the image generating circuitry 19, thestorage circuitry 25, and so on.

The tissue characterization is not limited to the attenuation constantaccording to analysis of the luminance value or the pixel value and maybe an amount reflecting the attenuation amount according to anotheranalysis. For example, when a plurality of ultrasonic waves forattenuation quantification having different frequencies are transmittedand received to and from one scanning line, the processing circuitry 29achieving the analysis function 299 executes frequency analysis based onDoppler data at a plurality of positions included in the non-structureregion and thereby may calculate a parameter showing the tissuecharacterization at a plurality of positions included in thenon-structure region. Specifically, the processing circuitry 29calculates as the tissue characterization a difference betweenattenuation amounts due to a difference in frequency with the use ofDoppler data corresponding to each of a plurality of ultrasonic wavesfor attenuation quantification.

When an ultrasonic wave in the band narrower than the frequency band inthe ultrasonic transmission concerning the B-mode is transmitted as theultrasonic wave for attenuation quantification to the subject P, theprocessing circuitry 29 executes frequency analysis with respect to dataobtained by reception of the ultrasonic wave for attenuationquantification in the narrow band. Subsequently, the processingcircuitry 29 calculates the attenuation amount as the tissuecharacterization, based on the frequency characteristics in thefrequency analysis.

The processing circuitry 29 achieving the display function allows themonitor 7 to display the tissue characterization as the analysis resultthereon. Specifically, the processing circuitry 29 outputs theattenuation constant data to the image generating circuitry 19. Theimage generating circuitry 19 generates an attenuation quantificationimage based on the attenuation constant data. At this time, theprocessing circuitry 29 controls the image generating circuitry 19 inorder to apply color phase corresponding to an attenuation constant inthe attenuation quantification image. By virtue of the control, theattenuation quantification image has the color phase corresponding tothe attenuation constant.

In a region corresponding to a position of a structure, the attenuationquantification image is in a state of being missed. Namely, theattenuation quantification image corresponding to the regioncorresponding to the position of the structure does not exist. The imagegenerating circuitry 19 outputs the attenuation quantification image tothe image compositing circuitry 23.

The image compositing circuitry 23 executes positioning (registration)between a B-mode image concerning a scanned region being substantiallythe same as the scanned region concerning collection of B-mode data forattenuation quantification and the attenuation quantification imageunder control by the processing circuitry 29. The image compositingcircuitry 23 converts the attenuation quantification image into apredetermined opacity or transparency under control by the processingcircuitry 29.

The image compositing circuitry 23 generates an attenuationsuperimposition image in which the attenuation quantification imagehaving a predetermined opacity or transparency is superimposed on aB-mode image. The image compositing circuitry 23 composites legendscorresponding to color phase of the attenuation constant on theattenuation superimposition image. The image compositing circuitry 23outputs the attenuation superimposition image on which the legends andso on are composited to the monitor 7.

The monitor 7 displays the attenuation amount as the analysis result ateach of a plurality of positions in a subject except for a position of astructure. Specifically, the monitor 7 displays the attenuationsuperimposition image on which the legends and so on are composited.

FIG. 4 is a view showing an attenuation superimposition image displayedon the monitor 7 together with legends. As shown in FIG. 4, in theattenuation superimposition image, the attenuation quantification imageis displayed in a state of being superimposed on a B-mode image at apredetermined opacity or transparency. As shown in FIG. 4, in theattenuation superimposition image, a region including an estimatedstructure position is a region which has a large variance ratio as shownin FIG. 3 and where the attenuation constant is not calculated, that is,a region where there is no attenuation quantification image. A B-modeimage of a back surface is displayed in this region. Namely, the regionincluding the structure position estimated in FIG. 4 includesstructures, such as blood vessels, an abdominal wall, and diaphragm, andregions near the structures and is a region where an attenuationquantification image (color image) showing an attenuation constant isnot displayed.

Hereinafter, a processing procedure concerning the structure estimationfunction and the tissue characterization analysis function will bedescribed. FIG. 5 is a flowchart showing an example of the processingprocedure concerning the structure estimation function and the tissuecharacterization analysis function.

The attenuation quantification start instruction is input by the inputapparatus 5 (Step Sa1). An ultrasonic wave for B-mode is transmitted andreceived to and from the subject P in response to the input of theattenuation quantification start instruction (Step Sa2). The processingin Step Sa1 may be executed after the processing in Step Sa2. At thistime, an operator inputs the attenuation quantification startinstruction when a B-mode image concerning analysis of an attenuationconstant is displayed with respect to the subject P. In addition, thestorage circuitry 25 may store a B-mode image generated in connectionwith the processing in Step Sa2 as shown in FIG. 2.

When B-mode data corresponding to one frame, that is, one scanned regionis collected, an ultrasonic wave for attenuation quantification istransmitted and received to and from the subject P (Step Sa3).Subsequently, B-mode data for attenuation quantification is generated. Aposition of a structure is estimated based on the B-mode data forattenuation quantification (Step Sa4). The structure position may beestimated based on the B-mode data generated after the processing inStep Sa2. At this time, a variance ratio superimposition image (see FIG.3) in which the variance ratio used in the estimation of the structureposition is superimposed on the B-mode image may be displayed on themonitor 7.

The tissue characterization (for example, the attenuation constant) at aplurality of positions except for the estimated structure position iscalculated based on the B-mode data for attenuation quantification (StepSa5). By virtue of the processing in Step Sa5, attenuation constant datain a scanned region being substantially the same as a scanned regionconcerning the B-mode image is generated. An attenuation quantificationimage is generated based on attenuation constant data showing anattenuation constant at each of a plurality of positions except for astructure position (Step Sa6). B-mode data is generated based on areception signal received in the processing in Step Sa2. Subsequently, aB-mode image is generated based on the B-mode data (Step Sa7).

The B-mode image and the attenuation quantification image arepositioned. In addition, a predetermined opacity or transparency isapplied to the attenuation quantification image. An attenuationsuperimposition image in which the attenuation quantification imagehaving a predetermined opacity or transparency is superimposed on theB-mode image is generated. The attenuation superimposition image isdisplayed on the monitor 7 (Step Sa8).

(Variation)

A variation differs from the above embodiment in that an attenuationquantification image corresponding to a scanned region concerningcollection of B-mode data for attenuation quantification is generated,and the attenuation quantification image at a structure positionestimated in the scanned region is not displayed in an attenuationsuperimposition image. In this variation, the processing of estimatingpartial data for attenuation quantification in the B-mode data forattenuation quantification is not required.

(Tissue Characterization Analysis Function)

The processing circuitry 29 achieving the gain reverse correctionfunction 295 subtracts reverse correction data from B-mode data forattenuation quantification. According to this constitution, theprocessing circuitry 29 generates the B-mode data for attenuationquantification before gain correction over the entire scanned region.

The processing circuitry 29 achieving the sound field characteristiccorrection function 297 subtracts sound field characteristic correctiondata from the B-mode data for attenuation quantification before gaincorrection. Consequently, the processing circuitry 29 generates theB-mode data for attenuation quantification (hereinafter referred to asattenuation B-mode data), which is not subjected to gain correction anddoes not depend on the sound field characteristics.

The processing circuitry 29 executing the analysis function 299 analyzesthe tissue characterization in the entire scanned region based on theattenuation B-mode data. Specifically, the processing circuitry 29calculates a differential value along a depth direction in a pixel value(or luminance value) in the attenuation B-mode data. The processingcircuitry 29 divides a value (attenuation amount), obtained bymultiplying the calculated differential value by ½ while considering twoways of ultrasonic waves, by the transmission center frequency of anultrasonic wave for attenuation quantification. By virtue of thedivision, the processing circuitry 29 calculates an attenuation constantat each of a plurality of pixels (positions) in a collection region.

By virtue of the above various calculations, the processing circuitry 29generates analysis data (attenuation constant data) showing anattenuation constant in the entire scanned region. The processingcircuitry 29 outputs the attenuation constant data to the imagegenerating circuitry 19 and the storage circuitry 25.

The processing circuitry 29 achieving the display function outputs theattenuation constant data to the image generating circuitry 19. Theimage generating circuitry 19 generates an attenuation quantificationimage to which color phase corresponding to an attenuation constant inan attenuation quantification image is applied, based on the attenuationconstant data. The size of the attenuation quantification image in thisvariation approximately corresponds to the size of a scanned region.

The image compositing circuitry 23 converts the attenuationquantification image into a predetermined opacity or transparency undercontrol by the processing circuitry 29. The image compositing circuitry23 generates an attenuation superimposition image in which theattenuation quantification image having a predetermined opacity ortransparency is superimposed on a B-mode image. The processing circuitry29 controls the image compositing circuitry 23 or the monitor 7 suchthat in display of the attenuation superimposition image, a partialregion of an attenuation quantification image corresponding to astructure position estimated in a scanned region is not displayed. Atthis time, the monitor 7 displays the attenuation superimposition imagein the form shown in FIG. 4, for example. Namely, the monitor 7 displaysthe analysis results obtained by the analysis function 299 with respectto a plurality of positions in a subject except for the structureposition estimated by the estimation function 293.

The processing circuitry 29 may control the image compositing circuitry23 or the monitor 7 such that the attenuation quantification image isdisplayed while masking the partial region in predetermined color phase.At this time, the monitor 7 displays the attenuation quantificationimage while masking the partial region in predetermined color phase.

The image generating circuitry 19 may generate a partial attenuationimage in which a partial region of an attenuation quantification imagecorresponding to a structure position estimated in a scanned region isremoved from the attenuation quantification image under control by theprocessing circuitry 29. At this time, the image compositing circuitry23 converts the partial attenuation image into a predetermined opacityor transparency under control by the processing circuitry 29. The imagecompositing circuitry 23 generates an attenuation superimposition imagein which the partial attenuation image having a predetermined opacity ortransparency is superimposed on a B-mode image. The monitor 7 displaysthe attenuation superimposition image.

Hereinafter, a processing procedure concerning the structure estimationfunction and the tissue characterization analysis function according tothis variation will be described. FIG. 6 is a flowchart showing anexample of a processing procedure concerning the structure estimationfunction and the tissue characterization analysis function according tothis variation. Since processing from Step Sb1 to Step Sb4 and Step Sb7is similar to the processing in Step Sa1 to Step Sa4 and Step Sa1 inFIG. 5, the description will be omitted.

An attenuation constant is calculated over a collection region based onB-mode data for attenuation quantification (Step Sb5). By virtue of theprocessing in Step Sb5, attenuation constant data in a scanned regionbeing substantially the same as a scanned region concerning a B-modeimage is generated. An attenuation quantification image is generatedbased on the attenuation constant data in a collection region (StepSb6).

An attenuation superimposition image in which the attenuationquantification image having a predetermined opacity or transparency issuperimposed on the B-mode image is generated (Step Sb8). Theattenuation superimposition image is displayed on the monitor 7 suchthat a region corresponding to a structure position in the attenuationquantification image in the attenuation superimposition image is notdisplayed or masked in predetermined color phase (Step Sb9).

According to the above described constitution, the following effects canbe obtained.

According to the ultrasonic diagnosis apparatus 1 of the presentembodiment and variation, the tissue characterization (such as theattenuation amount such as the attenuation constant, the modulus ofelasticity, the viscosity, and the hardness) can be displayed withrespect to a non-structure region by determining presence of astructure. Namely, according to the ultrasonic diagnosis apparatus 1,when the tissue characterization is displayed as a color image, a colornon-display state is achieved in a region where it is determined thatthere is a structure, and a B-mode image of the background can bedisplayed. Alternatively, according to the ultrasonic diagnosisapparatus 1, when the tissue characterization is displayed as a colorimage, in a region where it is determined that there is a structure, thetissue characterization can be displayed while being masked inpredetermined color phase different from the color image.

For example, comparing the attenuation superimposition image in FIG. 4displayed on the monitor 7 in the present embodiment and variation andan image in FIG. 11 in the prior art, in the image in FIG. 11, as aresult of calculation of attenuation constants in the entire regionregardless of presence of a structure, portions having various low andhigh attenuation constant values are displayed. Thus, in the image inFIG. 11, it is difficult to judge how much the attenuation constant of atissue to which attention of an operator is paid is. On the other hand,in the attenuation superimposition image in FIG. 4 displayed on themonitor 7 in the present embodiment and variation, since the tissuecharacterization in a region corresponding to a structure position isnot displayed, an operator can grasp a degree of attenuation showing thetissue characterization at first glance.

From the above, according to the ultrasonic diagnosis apparatus 1 of thepresent embodiment and variation, since reliable analysis results aredisplayed in a region except for an estimated structure position withoutallowing an operator to judge whether or not displayed images ornumerical values of the analysis results of the tissue characterizationare appropriate, the accuracy of obtained analysis results andreproducibility can be enhanced. In addition, according to theultrasonic diagnosis apparatus 1 of the present embodiment andvariation, in displayed images of the analysis results, since anoperator is not required to judge whether or not the displayed imagesare appropriate, a temporal or mental burden for the operator can bereduced, and diagnosis accuracy can be enhanced.

(First Application)

The present embodiment and the present variation differ in thatreliability of a representative value of an attenuation constant in ROI(hereinafter referred to as measurement ROI) set in an attenuationsuperimposition image displayed on the monitor 7 is determined, and therepresentative value is calculated and displayed according to thedetermination result. The measurement ROI is a region concerningcalculation of the representative value in the measurement ROI anddetermination of reliability for the representative value.

A setting function 291 has a function of setting the measurement ROI onan attenuation superimposition image displayed on the monitor 7. When anattenuation quantification image is displayed on the monitor 7, thesetting function 291 may set the measurement ROI on the attenuationquantification image. When a B-mode image is displayed on the monitor 7,the setting function 291 may set the measurement ROI on the B-modeimage.

An analysis function 299 has a function of calculating reliability forrepresentative values representing a plurality of attenuation constantsincluded in the measurement ROI, a function of comparing the reliabilityand a reliability determination threshold and thereby determining thereliability for a representative value, and a function of calculating arepresentative value concerning the measurement ROI when the reliabilityis larger than the reliability determination threshold.

A display function has a function of displaying the measurement ROI onan attenuation superimposition image on the monitor in response to inputof an instruction of starting measurement (hereinafter referred to as ameasurement start instruction) via the input apparatus 5 and a functionof displaying a representative value or predetermined notification onthe monitor 7 in response to the determination result obtained by theanalysis function 299.

The storage circuitry 25 stores programs concerning various functionsaccording to this application. The storage circuitry 25 storesreliability determination thresholds and predetermined notifications.The reliability determination threshold is a threshold for determinationof the reliability of the representative value calculated by theanalysis function 299. The predetermined notification is a characterstring or the like for notifying an operator or the like via the monitor7 of the fact that for example when the reliability is less than thereliability determination threshold, the representative value has noreliability, is not suitable, and cannot be measured.

The input apparatus 5 inputs the measurement start instruction by aninstruction from an operator. The input apparatus 5 inputs aninstruction of determining a position of the measurement ROI on anattenuation superimposition image displayed on the monitor 7 inaccordance with operator's operation via an interface such as atrackball or a panel button.

The processing circuitry 29 achieving the display function displays themeasurement ROI on the attenuation superimposition image displayed onthe monitor 7 in response to the measurement start instruction from anoperator via the input apparatus 5. The processing circuitry 29achieving the setting function 291 sets the measurement ROI on anattenuation superimposition image in response to a determinationinstruction from an operator via the input apparatus 5.

The processing circuitry 29 achieving the analysis function 299calculates the reliability for representative values representing aplurality of attenuation constants included in the measurement ROI,based on a pixel value included in the measurement ROI. Examples of therepresentative values include a mean value, median, and mode of aplurality of attenuation constants included in the measurement ROI on anattenuation quantification image.

Specifically, the processing circuitry 29 determines as an area of themeasurement ROI the number of pixels included in the measurement ROI(the number will be hereinafter referred to as a measurement pixelnumber). The processing circuitry 29 compares a plurality of varianceratios and a structure determination threshold included in themeasurement ROI and determines, as an area of a structure in themeasurement ROI, the number of pixels corresponding to the varianceratio larger than the structure determination threshold. The processingcircuitry 29 calculates a ratio of the area of the structure to the areaof the measurement ROI (the ratio will be hereinafter referred to as astructure area ratio). At this time, the reliability is, for example, adifference value obtained by subtracting an area ratio from 1.

The processing circuitry 29 may calculate a ratio of an area of anon-structure region to the area of the measurement ROI (the ratio willbe hereinafter referred to as a non-structure area ratio). In this time,the reliability corresponds to the non-structure area ratio.Specifically, the processing circuitry 29 compares a plurality ofvariance ratios and the structure determination threshold included inthe measurement ROI and determines, as a non-structure area in themeasurement ROI, the number of pixels corresponding to the varianceratio smaller than the structure determination threshold.

The reliability is not limited to the fact that it is based on thestructure area ratio or the non-structure area ratio calculated usingthe variance ratio. Namely, the reliability may be a ratio of the numberof pixels having color phase showing an attenuation constant to themeasurement pixel number. The reliability may be the variance ratiocalculated by the formula (2).

The reliability may be calculated such that the number of pixelsconcerning a luminance value higher than a predetermined luminance valuein a region included in the measurement ROI on a B-mode image withrespect to the measurement pixel number is taken to be the structurearea ratio. In this case, the predetermined luminance value is stored inthe storage circuitry 25. The predetermined luminance value is, forexample, a luminance value representing a structure such as the bloodvessel wall.

The reliability may be calculated such that the number of pixelsconcerning a luminance value lower than the predetermined luminancevalue in the region included in the measurement ROI on the B-mode imagewith respect to the measurement pixel number is taken to be thenon-structure area ratio. When the reliability is calculated usingB-mode data, the processing circuitry 29 allows a gain reversecorrection function 295, a sound field characteristic correctionfunction 297, and the analysis function 299 to generate attenuationconstant data with the use of the B-mode data used in calculation of thereliability.

The processing circuitry 29 compares the reliability and the reliabilitydetermination threshold and thereby determines the reliability for therepresentative value concerning the measurement ROI. Specifically, theprocessing circuitry 29 determines that measurement of a representativevalue in the measurement ROI is appropriate when the reliability islarger than the reliability determination threshold. The processingcircuitry 29 determines that measurement of the representative value inthe measurement ROI is not appropriate when the reliability is not morethan the reliability determination threshold.

When it is determined that measurement of the representative value inthe measurement ROI is appropriate, the processing circuitry 29calculates a representative value of the attenuation amount in themeasurement ROI based on the attenuation amount at each of a pluralityof positions in the measurement ROI. Specifically, the processingcircuitry 29 calculates representative values such as a mean value,median, and mode of attenuation constants, based on the attenuationconstants included in the measurement ROI. The processing circuitry 29may calculate the representative values with the use of a differentialvalue (hereinafter referred to as a mean differential value) obtained bydifferentiating a mean value of the measurement ROI in attenuation dataalong the depth direction. At this time, the following calculationprocedure is performed, for example.

First, the processing circuitry 29 averages a plurality of pixel valuesalong a plurality of scanning lines (hereinafter referred to as ameasurement scanning line) included in the measurement ROI in theattenuation data and thereby generates a measurement mean value. Then,the processing circuitry 29 averages a plurality of pixel values along ameasurement scanning line between an abutment surface in which anultrasonic probe 3 is abutted against a body surface of a subject P andthe measurement ROI and thereby generates an ROI upper mean value. Theprocessing circuitry 29 divides a value, obtained by differentiating themeasurement mean value from the ROI upper mean value, by a thickness ofthe measurement ROI along a center line of the measurement scanningline. The value according to this division corresponds to theabove-described mean differential value. Finally, the processingcircuitry 29 divides a value, obtained by multiplying the meandifferential value by ½ while considering two ways of ultrasonic waves,by the transmission center frequency of an ultrasonic wave forattenuation quantification and thereby calculates a representativevalue.

The processing circuitry 29 averages a plurality of pixel values along ameasurement scanning line in a region deeper than the measurement ROIand thereby may generate an ROI lower mean value. In this case, theprocessing circuitry 29 divides a value, obtained by differentiating theROI lower mean value from the measurement mean value, by the thicknessof the measurement ROI along the center line of the measurement scanningline. The value according to this division corresponds to theabove-described mean differential value.

The processing circuitry 29 controls the image compositing circuitry 23or the monitor 7 such that a representative value is displayed in ameasurement result display region in the monitor 7. In an image displayregion in the monitor 7, the measurement result display region isdifferent from a display region of an attenuation superimposition imageon which the measurement ROI is superimposed. The monitor 7 displays arepresentative value and the name of the measurement ROI in themeasurement result display region in addition to display of theattenuation superimposition image on which the measurement ROI issuperimposed.

When it is determined that measurement of the representative value inthe measurement ROI is not appropriate, the processing circuitry 29controls the image compositing circuitry 23 or the monitor 7 such that apredetermined notification is displayed in the measurement resultdisplay region. The monitor 7 displays a predetermined notification andthe name of the measurement ROI in the measurement result display regionin addition to display of the attenuation superimposition image on whichthe measurement ROI is superimposed.

FIG. 7 is a view showing an example in which when it is determined thatmeasurement of a representative value in measurement ROI1 is appropriateand measurement of a representative value in measurement ROI2 is notappropriate, a representative value and a predetermined notificationcorresponding to the name of the measurement ROI and an attenuationsuperimposition image on which the measurement ROI is superimposed aredisplayed on the monitor 7.

As shown in FIG. 7, the measurement ROI1 is set on a region includingthe uniform parenchyma of the liver, and an attenuation quantificationimage is displayed in the measurement ROI1. In such a case, since thereare few structures in the measurement ROI1, the attenuation constant canbe calculated with high accuracy in the measurement ROI1. Thus, as shownin FIG. 7, the names of the measurements ROI and a calculatedrepresentative value are displayed in a measurement result displayregion MDR.

On the other hand, as shown in FIG. 7, the measurement ROI2 is set in aregion including a vessel region, and an attenuation quantificationimage is not displayed in a majority of regions in the measurement ROI2.In such a case, since the attenuation constant cannot be calculated withhigh accuracy in the measurement 8012, a representative value is notcalculated. Thus, as shown in FIG. 7, the names of the measurements ROIand a predetermined notification “Not appropriate!” are displayed in themeasurement result display region MDR.

(Representative Value Calculation Function)

The representative value calculation function is a function ofdetermining the reliability of a representative value of an attenuationconstant in the measurement ROI and calculating and displaying therepresentative value in accordance with the determination result. Therepresentative value calculation function has a function ofcomprehensively achieving the above-described setting function 291,analysis function 299, and display function. The processing circuitry 29(processor) achieving the representative value calculation function mayfunction as a representative value calculation unit.

FIG. 8 is a flowchart showing an example of a processing procedureconcerning the representative value calculation function according tothe present application. The flowchart shown in FIG. 8 is a processingprocedure executed as a continuation of the flowchart in FIG. 5 or theflowchart in FIG. 6.

The measurement start instruction is input by the input apparatus 5(Step Sc1). The measurement ROI is displayed on an attenuationsuperimposition image displayed on the monitor 7 in response to theinput of the measurement start instruction. The measurement ROI is seton the attenuation superimposition image in response to input of thedetermination instruction (Step Sc2). A ratio of an area occupied by astructure in the set measurement ROI (structure area ratio) iscalculated (Step Sc3). The reliability is determined based on thestructure area ratio (Step Sc4).

If the reliability is more than the reliability determination threshold(Step Sc5), the representative value of the attenuation constant in themeasurement ROI is calculated (Step Sc6). Then, the representative valueis displayed in the measurement result display region (Step Sc7). If thereliability is less than the reliability determination threshold (StepSc5), a notification showing that measurement cannot be performed isdisplayed in the measurement result display region (Step Sc8). Theprocessing from Step Sc3 to Step Sc8 is repeated for each setting of themeasurement ROI. When a plurality of the measurements ROI are set on theattenuation superimposition image, the processing from Step Sc3 to StepSc8 is repeated with respect to each of the measurements ROI.

According to the above described constitution, the following effects canbe obtained in addition to the effects according to the presentembodiment and variation.

According to the ultrasonic diagnosis apparatus 1 of the presentapplication, when a representative value of the attenuation amount inthe measurement ROI designated by an operator is displayed, when thereare many structures included in the measurement ROI and when thestructure included in the measurement ROI is large, that is, when thedegree of reliability showing the reliability of a representative valueof numerical values showing the tissue characterization in themeasurement ROI is lower than the reliability determination threshold,the notification showing that measurement cannot be performed can bedisplayed without displaying the representative value. Namely, accordingto the ultrasonic diagnosis apparatus 1 of the present application, whenthere are many structures included in the measurement ROI or when thestructure included in the measurement ROI is large, a representativevalue of an attenuation constant in the measurement ROI is notdisplayed, regarding that the representative value is not reliable, andan operator can be prompted to set the measurement ROI again.

From the above, according to the ultrasonic diagnosis apparatus 1 of thepresent application, since reliable quantification results(representative values such as an attenuation constant showing thetissue characterization) are displayed, an operator is not required tojudge whether or not a displayed representative value is appropriate, atemporal or mental burden for the operator is reduced, and, in addition,reproducibility and accuracy of measurement of the tissuecharacterization can be enhanced.

(Second Application)

The second application differs from the first application in that arepresentative value corresponding to the measurement ROI is calculatedregardless of the reliability according to the presence of a structurein the measurement ROI, the area of the structure, or the like, and thereliability and representative value corresponding to the measurementROI are displayed.

The storage circuitry 25 stores at least one threshold (hereinafterreferred to as a rank threshold) configured to rank the reliability. Thenumber of rank thresholds is smaller by 1 than the number of ranks. Thestorage circuitry 25 stores a program concerning the ranking of thereliability (the program will be hereinafter referred to as a rankingprogram). When the reliability itself is displayed, the rank thresholdand the ranking program are not required.

The processing circuitry 29 achieving an analysis function 299calculates a representative value regardless of the reliability. Theprocessing circuitry 29 calculates the reliability corresponding to themeasurement ROI. The processing circuitry 29 reads out the rankthreshold and the ranking program from the storage circuitry 25. Theprocessing circuitry 29 compares the reliability and the rank thresholdin accordance with the ranking program and thereby ranks thereliability. Hereinafter, for ease of explanation, it is assumed thatthere are two rank thresholds (hereinafter referred to as a high rankthreshold and a low rank threshold). In this case, there are three ranks(for example, A, B, and C ranks). The number of the rank thresholds isnot limited to two. Namely, the number of the ranks is not limited tothree and may be arbitrarily set.

When the reliability is more than the high rank threshold, theprocessing circuitry 29 determines the rank of the reliabilityconcerning the measurement ROI as “A”. When the reliability is not morethan the high rank threshold and is more than the low rank threshold,the processing circuitry 29 determines the rank of the reliabilityconcerning the measurement ROI as “B”. When the reliability is not morethan the low rank threshold, the processing circuitry 29 determines therank of the reliability concerning the measurement ROI as “C”. Theprocessing circuitry 29 makes the determined rank correspond to themeasurement ROI related to the reliability and allows the storagecircuitry 25 to store the rank. The processing circuitry 29 controls theimage compositing circuitry 23 or a monitor 7 such that a representativevalue and a rank are displayed in a measurement result display region inthe monitor 7.

The monitor 7 displays a representative value, a rank, and the name ofthe measurement ROI in the measurement result display region in additionto display of an attenuation superimposition image on which themeasurement ROI is superimposed. The monitor 7 may display thereliability itself in the measurement result display region togetherwith the representative value and the name of the measurement ROI. Inthis case, the monitor 7 displays, as the reliability, the varianceratio calculated by the formula (2) or a non-structure area ratio, adifferential value obtained by differentiating a structure area ratiofrom 1, and the like.

FIG. 9 is a view showing an example in which representative values andthe ranks of reliability corresponding to the names of the measurementsROI and an attenuation superimposition image on which the measurementsROI are superimposed are displayed on the monitor 7. FIG. 9 shows anexample in which the reliability is displayed in three stages A, B, andC. As shown in FIG. 9, the measurement ROI1 is set on a region includingthe uniform parenchyma of the liver, and an attenuation quantificationimage is displayed in the measurement ROI1. In such a case, since thereare few structures in the measurement ROI1, the rank of the reliabilityis determined as “A” and displayed in a measurement result displayregion MDR together with a representative value concerning themeasurement ROI1.

As shown in FIG. 9, measurement ROI2 is set in a region including avessel region, and an attenuation quantification image is not displayedin a majority of regions in the measurement ROI2. In such a case, sincestructures exist in a majority of regions in the measurement ROI2, therank of the reliability is determined as “C” and displayed in themeasurement result display region MDR together with a representativevalue concerning the measurement ROI2.

(Reliability Display Function)

The reliability display function is a function of displaying thereliability or the rank of the reliability in the measurement resultdisplay region MDR together with a representative value calculatedregardless of the reliability according to the presence of a structurein the measurement ROI, the area of the structure, or the like. Thereliability display function has a function of comprehensively achievingthe setting function 291, the analysis function 299, and the displayfunction in the first application.

FIG. 10 is a flowchart showing an example of a processing procedureconcerning the reliability display function according to the presentapplication. The flowchart shown in FIG. 10 is a processing procedureexecuted as a continuation of the flowchart in FIG. 5 or the flowchartin FIG. 6. Since processing from Step Sd1 to Step Sd4 and Step Sd6 issimilar to the processing in Step Sc1 to Step Sc4 and Step Sc6 in FIG.8, the description will be omitted.

After the processing in Step Sd4, the reliability and the rank thresholdare compared, whereby the rank of the reliability is determined (StepSd5). When the reliability itself is displayed with a representativevalue, the processing in Step Sd5 is not required.

After the processing in Step Sd6, a representative value of anattenuation constant and the rank of the reliability are displayed inthe measurement result display region together with the name of themeasurement ROI (Step Sd7). The processing from Step Sd3 to Step Sd7 isrepeated for each setting of the measurement ROI. When a plurality ofthe measurements ROI are set on an attenuation superimposition image,the processing from Step Sd3 to Step Sd6 is repeated with respect toeach of the measurements ROI, and representative values and rankscorresponding to the respective measurements ROI are listed in themeasurement result display region.

According to the above described constitution, the following effects canbe obtained in addition to the effects according to the presentembodiment and variation.

According to the ultrasonic diagnosis apparatus 1 of the presentapplication, when a representative value of the attenuation amountincluded in the measurement ROI is displayed, the reliabilitycorresponding to the size and degree of a structure included in themeasurement ROI can be displayed together. Namely, according to theultrasonic diagnosis apparatus 1 of the present application, even when aplace where a reliable result is obtained by the tissue characterizationof a target tissue is hardly found in the measurement ROI, certainquantification results (representative values) can be obtained. Forexample, in cases in which the entire liver is nonuniform, such as acase in which fibrosis has progressed, attenuation quantificationresults (representative values) can be displayed together with thereliability in any place.

From the above, according to the ultrasonic diagnosis apparatus 1 of thepresent application, since the level of reliability of a quantificationresult can be displayed, an operator can refer to the quantificationresult as reference information at ease and use the quantificationresult in diagnosis.

(Third Application)

The third application differs from the present embodiment and variationand the first and second applications in that an MRI apparatus isapplied as a medical diagnostic apparatus. A calculator in the MRIapparatus (not shown) includes the image generating circuitry 19, theimage memory 21, the image compositing circuitry 23, the storagecircuitry 25, the interface circuitry 27, the processing circuitry 29,and a sequencer (not shown). The calculator is connected to an inputapparatus 5, a monitor 7, and so on.

The processing circuitry 29 in the calculator executes various functionsas described above. The storage circuitry 25 in the calculator storesvarious data such as programs concerning various functions executed bythe processing circuitry 29.

The processing circuitry 29 achieving an estimation function 293 in thisapplication estimates a position of a structure in a cross sectioncorresponding to MR (Magnetic Resonance) scanning, based on dataobtained by MR scanning (the data will be hereinafter referred to as MRdata) utilizing a magnetic resonance phenomenon, as described above.

The processing circuitry 29 achieving an analysis function 299 in thisapplication analyzes the tissue characterization at a plurality ofpositions in a subject except for a structure position estimated by theestimation function 293 in a cross section, based on data obtained by MRscanning utilizing the nuclear magnetic resonance phenomenon. The tissuecharacterization in this application is an amount showingcharacterization of a tissue to be diagnosed, such as the attenuationamount, modulus of elasticity (Young's modulus), viscosity, anddistortion. In this application, for example, the tissuecharacterization is obtained by MR elastography (MRE). At this time,data concerning analysis of the tissue characterization corresponds toMRE data obtained by MRE scanning.

Hereinafter, for ease of explanation, MRE is taken to be an elastographymethod of observing a wave propagating inside a subject P with the useof a phase image in which an image of a phase of a proton is created,based on vibration due to a nonmagnetic vibration mechanism providedoutside the subject P.

The image generating circuitry 19 in the calculator generates an MRimage based on MR data obtained by MR scanning executed with respect tothe subject P under control by the sequencer. Further, the imagegenerating circuit 19 generates an MRE image based on MRE data obtainedby MRE scanning executed with respect to the subject P under control bythe sequencer. The MR image or the MRE image is used in a settingfunction 291 and the estimation function 293. The MRE image is furtherused in the analysis function 299.

In this application, in an attenuation superimposition image displayedon the monitor 7, the background image in FIG. 4 is the MR image, and anattenuation quantification image corresponds to the MRE image. Since aprocessing procedure concerning a structure estimation function and atissue characterization analysis function according to this applicationis substantially similar to FIG. 5, different processing will bedescribed. The MR image and the MRE image may not be displayed to besuperimposed but may be individually displayed.

In this application, the processing corresponding to Step Sa2 in FIG. 5is processing for executing MR scanning with respect to the subject P inaccordance with an imaging sequence for collecting MR data. In thisapplication, the processing corresponding to Step Sa3 in FIG. 5 isprocessing for executing MRE scanning with respect to a subject inaccordance with an imaging sequence for collecting MRE data.

In this application, the processing corresponding to Step Sa4 in FIG. 5is processing for estimating a position of a structure based on the MREdata. In this application, the processing corresponding to Step Say inFIG. 5 is processing for calculating an attenuation constant based onthe MRE data at a plurality of positions except for a position of astructure.

In this application, the processing corresponding to Step Sa1 in FIG. 5is processing for generating an MR image. In this application, theprocessing corresponding to Step Sa8 in FIG. 5 is processing forperforming display while superimposing an attenuation quantificationimage on an MR image.

According to the MRI apparatus of this application, it can be similarlyexecuted in the variation of the present embodiment, the firstapplication, and the second application.

According to the above-described constitution, the following effects canbe obtained as in the present embodiment and variation.

According to the MRI apparatus of this application, the tissuecharacterization can be displayed with respect to a non-structure regionby determining the presence of a structure. Namely, according to the MRIapparatus, when the tissue characterization is displayed as a colorimage, a color non-display state is achieved in a region where it isdetermined that there is a structure, and an MR image of the backgroundcan be displayed. Alternatively, according to the MRI apparatus, whenthe tissue characterization is displayed as a color image, in a regionwhere it is determined that there is a structure, the tissuecharacterization can be displayed while being masked in predeterminedcolor phase different from the color image.

From the above, according to the MRI apparatus of this application,since reliable analysis results are displayed in a region except for anestimated structure position without allowing an operator to judgewhether or not displayed images or numerical values of the analysisresults of the tissue characterization are appropriate, the accuracy ofobtained analysis results and reproducibility can be enhanced. Inaddition, according to MRI of this application, in displayed images ofthe analysis results, since an operator is not required to judge whetheror not the displayed images are appropriate, a temporal or mental burdenfor the operator can be reduced, and diagnosis accuracy can be enhanced.

In addition, each function associated with each embodiment can also beimplemented by installing programs for executing the correspondingprocessing in a computer such as a workstation and mapping them in amemory. In this case, the programs which can cause the computer toexecute the corresponding techniques can be distributed by being storedin recording media such as magnetic disks (hard disks and the like),optical disks (CD-ROMs, DVDs, and the like), and semiconductor memories.

According to the above-described medical diagnostic apparatus andmedical analysis method, the tissue characterization in the subject P isanalyzed, and the tissue characterization in a non-structure region inthe subject can be displayed.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

The invention claimed is:
 1. A medical diagnostic apparatus comprising:processing circuitry configured to estimate a position of a structure ina subject based on data obtained by scanning with respect to the subjectand to analyze tissue characterization corresponding to attenuation ofan ultrasonic wave propagating in the subject based on the data used forestimating the position of the structure; and display circuitryconfigured to display an analysis result of the tissue characterizationobtained by the processing circuitry with respect to a plurality ofpositions in the subject except for the estimated position of thestructure.
 2. The medical diagnostic apparatus according to claim 1,wherein the processing circuitry is configured to estimate the structureposition based on the data obtained by ultrasonic scanning with respectto the subject, and to analyze the tissue characterization at thepositions based on the data obtained by the ultrasonic scanning withrespect to the subject.
 3. The medical diagnostic apparatus according toclaim 2, wherein the processing circuitry is configured to set aplurality of regions in a scanning region in the ultrasonic scanning, tocalculate a variance value and a mean value based on the data in each ofthe regions, and to estimate the structure position in the scanningregion based on the variance value and the mean value.
 4. The medicaldiagnostic apparatus according to claim 2, wherein the processingcircuitry is configured to estimate the structure position in thescanning region by executing contrast false alarm rate processing withrespect to a scanning region in the ultrasonic scanning.
 5. The medicaldiagnostic apparatus according to claim 2, wherein the processingcircuitry is configured to calculate, as the tissue characterization, afeature quantity concerning an attenuation amount of the ultrasonic wavepropagating in the subject, and the display circuitry is configured todisplay the attenuation amount as the analysis result at each of aplurality of positions in the subject except for the structure position.6. The medical diagnostic apparatus according to claim 5, furthercomprising input interface circuitry configured to input a region ofinterest to an ultrasonic image corresponding to the ultrasonicscanning, wherein the processing circuitry is configured to calculate arepresentative value representing the attenuation amount in the regionof interest, based on the attenuation amount at each of a plurality ofpositions in the region of interest, and the display circuitry isconfigured to display the representative value with the region ofinterest.
 7. The medical diagnostic apparatus according to claim 6,wherein the processing circuitry is configured to calculate a degree ofreliability concerning the representative value based on a pixel valuein the region of interest, and the display circuitry is configured todisplay the reliability with the representative value.
 8. The medicaldiagnostic apparatus according to claim 5, wherein the processingcircuitry is configured to cancel gain correction with respect to thedata, to cancel dependency of sound field characteristics in the databased on the sound field characteristics in the ultrasonic scanning, andto calculate the attenuation amount as the tissue characterization basedon correction data in which the gain correction and the dependency ofthe sound field characteristics are cancelled in the data.
 9. Themedical diagnostic apparatus according to claim 5, further comprisingultrasonic transmitting circuitry configured to transmit a plurality ofultrasonic waves having different frequencies to the subject in theultrasonic scanning, wherein the processing circuitry is configured tocalculate, as the tissue characterization, a difference between theattenuation amounts due to the difference in frequency with the use ofthe data corresponding to each of the ultrasonic waves.
 10. The medicaldiagnostic apparatus according to claim 5, further comprising ultrasonictransmitting circuitry configured to transmit an ultrasonic wave in aband narrower than a frequency band in ultrasonic transmissionconcerning a B-mode in the ultrasonic scanning, wherein the processingcircuitry is configured to execute frequency analysis with respect todata obtained by reception of the ultrasonic wave in the narrow band,and to calculate the attenuation amount based on frequencycharacteristics in the frequency analysis.
 11. The medical diagnosticapparatus according to claim 5, wherein the display circuitry isconfigured to perform display such that the attenuation amount issuperimposed on a B-mode image in color phase corresponding to a valueof the attenuation amount at a predetermined opacity or transparency.12. The medical diagnostic apparatus according to claim 1, wherein theprocessing circuitry is configured to calculate at least one ofviscosity of a tissue in the subject and elasticity of the tissue. 13.The medical diagnostic apparatus according to claim 1, wherein theprocessing circuitry is configured to estimate the structure positionbased on data obtained by scanning using a nuclear magnetic resonancephenomenon as the scanning, and to analyze the tissue characterizationat the positions based on the data obtained by the scanning using thenuclear magnetic resonance phenomenon.
 14. The medical diagnosticapparatus according to claim 1, wherein the processing circuitry isconfigured to generate a B-mode image based on the data, and the displaycircuitry is configured to display the analysis result on the B-modeimage.
 15. A medical diagnostic apparatus comprising: processingcircuitry configured to estimate a position of a structure in a subjectbased on data obtained by scanning with respect to the subject, and toanalyze tissue characterization corresponding to elasticity or viscosityof a tissue in the subject based on the data used for estimating theposition of the structure, wherein the tissue characterization isobtained from propagation velocity of a shear wave generated in thesubject, and display circuitry configured to display an analysis resultof the tissue characterization obtained by the processing circuitry withrespect to a plurality of positions in the subject except for theestimated position of the structure.
 16. A medical analysis methodcomprising: estimating a position of a structure in a subject based ondata obtained by scanning with respect to the subject; analyzing tissuecharacterization corresponding to elasticity or viscosity of a tissue inthe subject based on the data used for estimating the position of thestructure, wherein the tissue characterization is obtained frompropagation velocity of a shear wave generated in the subject; anddisplaying, on a monitor, an analysis result of the analyzed tissuecharacterization with respect to a plurality of positions in the subjectexcept for the estimated position of the structure.